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Proposal for Professional Engineering Services Sessom Creek Erosion Remediation Evaluation In 2011, the City completed street and drainage improvements in Sessom Drive that included pavement repairs, cross culverts and several new curb inlets. An update to the City's master drainage plan is scheduled in the City's 2013 fiscal budget /year. Stream Erosion - Aside from the natural erosion process that defines the bed and banks of an earthen stream, the creek is experiencing several severe forms of erosion and failures throughout its length. In the headwaters of Sessom Creek (upstream of LBJ Drive) where the channel is more natural, the creek is incised in several reaches, tributary streams are head - cutting and structural elements are experiencing erosion at the margins. In the urban reach downstream of LBJ Drive, the existing slope paving is experiencing structural failures that will ultimately undermine the structural integrity of the channel as well as adjacent structures. Water Quality — With respect to water quality, during a field trip in March 2012, some algae was present in the stream bed upstream of LBJ Drive and there was evidence of paint disposal into the creek from Sessom Drive. At one point, the creek flows under a residential road and chunks of asphalt are breaking off and traveling downstream into the San Marcos River. It appears that most rainfall runoff from developed areas discharge directly into the system without treatment. In other words, pollutants such as oil and grease, pesticides and herbicides, etc. will flow directly to Sessom Creek and be conveyed downstream. While sedimentation basins have been constructed to the west of the intersection of Sessom Drive and Aquarena Springs Drive to intercept sediment and pollutants prior to discharge to the San Marcos River, sediment has still accumulated at the outfall of Sessom Creek at the headwaters of the San Marcos River. Although sediment and sediment transport is typically a natural element of a dynamic stream system, in this case, urbanization has increased the quantity of sediment and its impacts on the receiving stream (San Marcos River) may be detrimental. For example, Texas wild -rice, which naturally occurs in the headwaters of the San Marcos River, has been listed as endangered species by the US Fish and Wildlife Service and recently deemed a "state protected species" by Texas Parks and Wildlife Service, and requires "clear and clean flowing water in order to survive and remain viable." While it appeared during the field trip that the sedimentation basins where somewhat effective in removing pollutants, their efficiency is unknown. In 2013, the City, through the Edwards Aquifer Recovery Program (EARIP), will develop a Water Quality Protection Plan (WQPP) for the Upper San Marcos River which will identify pollutant sources and establish priority watersheds for San Marcos including Sessom Creek. WORK BREAKDOWN STRUCTURE The following work breakdown structure includes a series of specific tasks to complete this project. Data Collection — RPS Espey will obtain additional topographic and environmental information from the City of San Marcos (including detailed topographic survey along Sessom Drive to LBJ Drive), Texas State University (TSU), Edwards Aquifer Authority (EAA), US Geologic Survey (USGS) and others in order to conduct the analyses and assessments described in this scope of services. RPS Espey will walk the entire project length, make an initial assessment and document the current state of erosion for the overall system as well as at discrete locations. This includes structural failures along the concrete lined portions of the channel, erosion at transitions between concrete and earthen stream Page 2 of 7 September 18, 2012 Revised October 9, 2012